# All Questions

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### How is the ambiguity in code phase resolved in GNSS code-based positioning?

For positioning using GNSS, a typical introduction text (example PDF) introduces the concept of pseudo ranges as roughly being the time between transmission of a GNSS signal by the satellite $s$ and ...
27 views

### Computationally solving the two-body problem for patched conics approximation

I have been trying to create an orbital simulation using the patched conics approximation like Kerbal Space Program. I initially tried solving Kepler's equation using Newton's method, however this ...
72 views

### Why is the hot side of the James Webb Space Telescope expected to be 85 C?

According to multiple sources, the heat shield on JWST is expected to exceed 85 °C. The average temperature of the earth is only 15 °C, so this is about 70 °C higher at roughly the same distance from ...
36 views

### Suppose I wanted to compare TLEs to actual LEO satellite positions, what data is available? From which may it be easiest to extract X, Y, Z, T points?

Under @RyanC's answer to How can I plot satellite's trajectory from three different TLEs to detect any deviation on path with time? I wrote: I think that SGP4 + TLEs is so popular because the TLEs ...
172 views

### If Voyager 1 were to return to the Earth now, how much "younger" it would be than its replica displayed at JPL's Von Karman Auditorium?

Just out of curiosity, based on Einstein's special relativity theory, if Voyager were to return to the Earth now at the same average speed at which it flew to its current position, how much "...
70 views

### Is RCS a good option to control roll during the atmospheric phase of the launch vehicle?

Do rcs perform well in the presence of high aerodynamic forces?
2k views

### Why are eclipses of the James Webb by the Earth or Moon not permitted during the mission?

Why are eclipses of the James Webb Space Telescope (JWT) by the Earth or Moon not permitted during the mission? In Seasonal variations of the James Webb Space Telescope orbital dynamics it is stated ...
66 views

### How will SpaceX build a SuperHeavy launch mount at LC39A, and active launch pad?

We have seen how fast SpaceX built the Boca Chica launch mount. We also saw the approach of building the base, then lifting segments built offsite (At the gas well site) to assemble them. However, as ...
98 views

### The design of the halo orbit of the James Webb Space Telescope

As I feel a little less uncomfortable with "halo" orbits, with this question, I would like to explore the practical aspects, in particular those related to the design of the James Webb Space ...
43 views

### Which S-Band ISS antenna stopped transmitting to TDRS and was replaced during the recent 2021-12-02 EVA?

CNN's says: Marshburn and Barron began their spacewalk at 6:15 a.m. ET, and it's expected to last for about six and a half hours. The team will replace a malfunctioning communications antenna. Live ...
55 views

### Since we humans are't able to process any dimensions like 4D and 5D, the distance between stars and galexies appers to be too far away [duplicate]

For exmaple a living oraganism of 2D world is unable to perseive a 3D world. Similary, do humans have such limitations to perseive the further dimensions that 3D, that could results in wrong ...
114 views

### Neutron boosters second stage inside the fairing, is this unique?

RocketLabs announced info about the new Neutron booster. Neutron Booster video Many interesting aspects summarized as: The landing legs do not deploy, but are permanently mounted around a relatively ...
185 views

### What is this black smoke coming from an all solid fueled Epsilon rocket?

I saw a clip of a recent (Nov. 5th, 2021) JAXA Epsilon launch on Instagram (link). Shown differently here in a YouTube video @~0:23s: It's an entirely solid fueled ...
55 views

### Could a car drive to the Moon?

Once you've got past the headline which sounds immediately ridiculous, consider this scenario: In the film Back to the Future, Doc powered his DeLorean by a little Mr. Fusion unit. If we assume that ...
74 views

### Material used in LOX propellant tank

Most launch vehicles use aluminum alloy AA2219 for LOX propellant tanks, has anyone used AA6061 with additional coating instead?
244 views

### What is different between Hill frame and LVLH frame in satellite?

What is different between Hill frame and local-vertical, local-horizontal (LVLH) frame in satellite? I add one figure to show this two frame. reference of figure: Weiss, Avishai, Uroš V. Kalabić, ...
188 views

### Why are there six orbital elements?

I have knew for a long time that there were six orbital elements but I never knew why it was six and not any other arbitrary number? Does it have do with the fact that there is 3 components for both ...
22 views

### How to calculate the goldilocks zones of brown dwarf stars? Do any encroach on the stars' Roche limit? [migrated]

Ignoring tidal heating and such, how can one calculate the habitable orbital ranges for M, L, T, and Y spectral class stars? The reason I ask is that I'm also curious if any of these zones encroach ...
3k views

Prompted by Scott Manley's recent video on escape vehicles I wondered: Has there ever been a moment where someone was on board a space station but without access to a vehicle that could return them ...
63 views

### How long does it take for the ISS astronauts to isolate a module

In the chosen answer for What size hole in the International Space Station would be catastrophic, we find that a 0.6cm hole would depressurize the ISS to life threatening levels in 14 hours. A 20cm ...
1k views

### How were registers in the Apollo Guidance Computer implemented?

I'm having a hard time finding information on the composition of the AGC's registers. Were they also Magnetic Core Memory or something else?
39 views

### Designing of CD nozzle with respect to Mass flow rate of propellants

How do I calculate the flow rate of exhaust gases required at the throat of a CD nozzle, with given throat diameter of "D", so as to achieve a "Choked flow condition" (velocity of ...
384 views

### Nitrogen pentoxide oxidiser?

Both dinitrogen oxide and nitrogen tetroxide are used in storable propellant combinations, so, simply as a continuation, can the larger nitrates (N2O5, N2O6, etc.) still be used in an engine. Is it ...
58 views

### How we can relate rotary inverted pendulum to a rocket system?

Initially I posted this question on EE Stack Exchange but I am also posting it here in Space Stack Exchange so I may get attention from a much related audience. I am interested in control systems ...
54 views

### Training ML models in space

It's not really space exploration unless space crews need to train new machine learning (ML) models for some new problems they face during their journey but I read this: https://www.technologyreview....
3k views

### Could an electromagnet be used to raise the apogee of a satellite orbiting Earth?

Suppose we have a satellite orbiting Earth in an elliptical orbit, which has an electromagnet inside it. As the satellite goes from its apogee to its perigee (i.e. losing altitude), it turns on the ...
234 views

### What size hole in the International Space Station would be catastrophic?

I was reading "Russia threatens criminal charges against a NASA astronaut" in arstechnica.com. Somewhere in the article it says: " At the time, a 2 mm breach was discovered in the ...
9k views

### Shouldn't space junk fall back to Earth on its own? How long will take for a ~1 cm piece of junk in LEO to fall back to Earth on its own for example?

I'm a noob in this subject and know little about space exploration, but I wonder about this every time I read the news: Wouldn't drag make all space junk fall back to Earth after some time? I'm ...
209 views

Could Apollo's Sextant navigation for Cislunar Celestial Navigation use similar geometry as Marine Navigation? My grandfather would be familiar with the instrument in this astronaut’s hands, although ...
163 views

### Nuclear or Solar power for satellites?

For satellites do they use solar or nuclear for the main power source? I do know that they have both but I do not know which is primary. for an example: Galileo, does it use solar or nuclear?
137 views

### Can we infer things beyond the observable universe? [closed]

Is it possible to infer information about the structure of the universe beyond the observable one, by observing its effects on the parts we can see? Can for example gravity from sources we cannot see ...
60 views

### Study of selection higher stages for a multistage rocket

Will it be correct to say that the thrust produced by the first stage is the ultimate limiting factor for a rocket's ability? The logic behind this thought is like this: Higher quantity of its ...
382 views

### How much did we know about space in 1940? [closed]

I'm reading a thoroughly ridiculous book, Calling Captain Future. It was written as a pulp serial in the 1940's, and is set in a very futuristic 1990. In addition to its many rather entertaining ...
57 views

### How to calculate the force applied by a magnetorquer on a piece of a perfect ferromagnetic material?

How to calculate the force applied by a magnetorquer on a piece of a perfect ferromagnetic material at a particular distance in vacuum given that I know the actuatuon (in Am2) https://www.isispace.nl/...
74 views

### How to sort orbital positions in the order of following by spacecraft?

I have an orbiting spacecraft which keplerian elements is known. Also, I have a random-ordered list of true anomalies that represents spacecraft's positions on that orbit. How to sort this list to get ...
96 views

### How would a 6.2 quadrillion kilogram object sitting on the surface of the earth affect it's gravity? [closed]

Why so specific you may ask. Doesn't matter, it's just a physics issue I'm figuring out how to fix for my calculations that I'm working on. I'm wondering as to how a block of star matter would affect ...
67 views

### Do operational Starlink satellites run their ion engines at night on batteries? And if so, do they have hi/low settings?

Discussion below What is the maximum thrust of the Starlink satellites? raise the question of the Starlink communications satellites' power budget and use of their ion thruster in daylight when the ...
18 views

### Radio coherent transponders are the foundation of deep space navigation, have optical analogues been used? If so, the furthest distance measured?

Coherent radio transponders receive a signal from Earth containing specially encoded modulation, amplify it and retransmit it back to Earth. Correlating the received signal with the transmitted signal ...
72 views

### Long lived solar powered rovers without radioisotope heater units (like Zhurong), for use beyond Mars

The Yutu rovers use RHUs to stay warm and survive the two week long lunar nights, every other rover uses nuclear material as well (except Sojourner), but the Zhurong rover uses a novel storage-heating ...
162 views

### Why aren’t vacuum engines turned on after Mach 1?

In rockets, smaller nozzles are used at lower altitudes because atmospheric pressure would cause problems by pushing air into nozzles with higher expansion ratios. However, it seems to me that once ...
2k views

### Has ion propulsion ever been used in a deep space trajectory correction maneuver proper?

Answer(s) to What types of propulsion are used to adjust an orbit? lead me to wonder if electric propulsion has ever been used for a proper TCM or "trajectory correction maneuver" in deep ...
29 views

### How many solar system bodies have had their magnetic fields directly measured?

Discussion below this post lead me to wonder: Question: How many solar system bodies have had their magnetic fields directly measured? Inferences from radio or spectroscopic observations don't count ...
392 views

### What types of propulsion are used to adjust an orbit?

What types of propulsion are used to adjust the orbit of an object such as a satellite, space station, supply vehicle? I'm curious if they all use the same method to adjust their trajectory, or if ...
93 views

### What is the maximum thrust of the Starlink satellites?

As in the title, what is the maximum thrust (in N) that the satellites of the Starlink constellation can achieve? I read that they use Hall-effect thrusters, but I couldn't find a specification of the ...
101 views

### Are Elon Musk's SpaceX rockets better than the Russian rockets? [closed]

What are the advantages and disadvantages of SpaceX rockets VS Russian rockets?
78 views

### How to calculate the Lagrangian points positions?

I have two bodies, one rotates around another on orbit. For i.e. Earth and Sun or Moon and Earth. If we know masses, velocity, distance and keplerian elements of orbit, how can we find the positions ...
214 views

### How come satellites and space stations that travel through space at Earth's speed do not disintegrate?

What I mean, if Earth travels through space at 1,700 km/hour, when a spaceship or other object leaves its atmosphere, should it not stay behind? And if it is gravity that keeps it near Earth, should ...
79 views

### Do reversible proton-exchange membrane hydrolizer/fuel cells exist? Have they been incorporated into a “Hydrogen Battery”?

Solar power on the Moon suffers from the month-long Lunar rotation which necessitates enough energy storage to last through the 2 week Lunar night. An alternative to battery storage would be a closed-...